a) We know that
Power = P = VI
that is curve of power will be having maximum amplitude, equals to multiplication of amplitudes of voltage (V) and current (I) curve. So, the curve will be represented by A.
b) As shown by shaded area in the diagram, the full cycle of the graph consists of one positive and one negative symmetrical area.
Hence, average power over a cycle is zero.
c) As the average power is zero, hence the device may be inductor (L) or capacitance (C) or the series combination of L and C.